1. Field of the Invention
The present invention relates generally to the field of optoelectronic devices and, more particularly, to devices which function as extremely high speed optical shutters, and to applications of such devices.
2. Description of the Related Art
A number of important commercial, scientific, medical and military signal processing or sampling applications require high speed conversion of time-varying analog waveforms into digital form. Such higher digitization speed is useful because, among other reasons, it provides better spatial resolution for lidar and range-finding, better time resolution for clock synchronization protocols, better instrumental resolution for sampling oscilloscopes, and better channel separation for wideband receivers. Higher speed analog-to-digital (A/D) converters are additionally sought because there is often a threshold conversion rate below which the application requiring the samples is infeasible, such as digital receivers operating in a particular microwave band.
It is known that an analog serial-to-parallel (S/P) converter can be used to parcel out portions of a time-varying waveform to parallel A/D converters working in parallel. In such systems, the quality of the S/P converter stage bounds the subsequent fidelity of the overall converter, so manufacturability and control of noise are crucial considerations. Unfortunately, today's all-electronic S/P converters operate well below 60 gigasamples per second (GSPS), which is not much faster than today's state-of-the-art electronic A/D converters (e.g., 6 GSPS claimed by Rockwell in the laboratory, for which, to applicants' knowledge, no publicly-available enabling disclosure exists), so there is little fan-out by the S/P converter. By way of comparison, all-optical switching/sampling phenomena can occur at intrinsically higher speeds than analogous electronic phenomena, since electron mobility in the solid state is up to 10,000-fold slower than the speed of light; the advantage is lessened by the ratio of device sizes.